US9148079B2 - Method for operating an electric motor - Google Patents

Method for operating an electric motor Download PDF

Info

Publication number
US9148079B2
US9148079B2 US14/143,664 US201314143664A US9148079B2 US 9148079 B2 US9148079 B2 US 9148079B2 US 201314143664 A US201314143664 A US 201314143664A US 9148079 B2 US9148079 B2 US 9148079B2
Authority
US
United States
Prior art keywords
electric motor
temperature
steering system
electric
power steering
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Active, expires
Application number
US14/143,664
Other languages
English (en)
Other versions
US20140210394A1 (en
Inventor
Thomas Kuehnhoefer
Alexander Krautstrunk
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Robert Bosch Automotive Steering GmbH
Original Assignee
Robert Bosch Automotive Steering GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Robert Bosch Automotive Steering GmbH filed Critical Robert Bosch Automotive Steering GmbH
Assigned to ZF LENKSYSTEME GMBH reassignment ZF LENKSYSTEME GMBH ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: KRAUTSTRUNK, ALEXANDER, KUEHNHOEFER, THOMAS
Publication of US20140210394A1 publication Critical patent/US20140210394A1/en
Assigned to ROBERT BOSCH AUTOMOTIVE STEERING GMBH reassignment ROBERT BOSCH AUTOMOTIVE STEERING GMBH CHANGE OF NAME (SEE DOCUMENT FOR DETAILS). Assignors: ZF LENKSYSTEME GMBH
Application granted granted Critical
Publication of US9148079B2 publication Critical patent/US9148079B2/en
Active legal-status Critical Current
Adjusted expiration legal-status Critical

Links

Images

Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P7/00—Arrangements for regulating or controlling the speed or torque of electric DC motors
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
    • B62D—MOTOR VEHICLES; TRAILERS
    • B62D5/00—Power-assisted or power-driven steering
    • B62D5/04—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear
    • B62D5/0457—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear characterised by control features of the drive means as such
    • B62D5/046—Controlling the motor
    • B62D5/0463—Controlling the motor calculating assisting torque from the motor based on driver input
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
    • B62D—MOTOR VEHICLES; TRAILERS
    • B62D5/00—Power-assisted or power-driven steering
    • B62D5/04—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear
    • B62D5/0457—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear characterised by control features of the drive means as such
    • B62D5/0481—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear characterised by control features of the drive means as such monitoring the steering system, e.g. failures
    • B62D5/0496—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear characterised by control features of the drive means as such monitoring the steering system, e.g. failures by using a temperature sensor
    • H02P29/0055—
    • H02P29/0066—
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P29/00—Arrangements for regulating or controlling electric motors, appropriate for both AC and DC motors
    • H02P29/60—Controlling or determining the temperature of the motor or of the drive
    • H02P29/64—Controlling or determining the temperature of the winding
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P29/00—Arrangements for regulating or controlling electric motors, appropriate for both AC and DC motors
    • H02P29/60—Controlling or determining the temperature of the motor or of the drive
    • H02P29/66—Controlling or determining the temperature of the rotor
    • H02P29/662—Controlling or determining the temperature of the rotor the rotor having permanent magnets

Definitions

  • the invention relates to a method for operating an electric motor and to a method for operating an electronic power steering system of a motor vehicle.
  • the invention additionally relates to an electronic power steering system of a motor vehicle and to an electronic control unit of such an electronic power steering system.
  • a steering system is known from DE 100 13 711 A1, which includes a servo drive for torque assistance (power steering).
  • the degree of torque assistance in the described steering system is dependent on the vehicle speed. While the torque assistance is greater at a low vehicle speed (for example, so as to be able to operate the steering wheel without great effort when maneuvering the vehicle), the torque assistance is lowered at higher speeds (for example so as to increase driving stability when driving on a highway).
  • the servo drive can be operated electrically or hydraulically.
  • the steering system described in DE 100 13 711 A1 also comprises superimposition means, which generate an additional angle and superimpose this additional angle on the steering wheel angle predetermined by the steering handle.
  • the electric motors used typically comprise high-performance magnets.
  • the permanent magnets or magnetic elements notably can lose the magnetic properties thereof in a manner that is entirely or partially irreversible if they are exposed to corresponding temperatures and opposing magnetic fields generated by electrical current.
  • the magnets in electric motors must therefore be designed for extreme or maximum ambient requirements in terms of temperatures or opposing fields.
  • the temperatures of the magnetic elements can usually not be directly measured during the operation of the electronic power steering system. Rare earth magnets are demagnetized more quickly at high temperatures, while ferrite magnets are demagnetized more quickly at cold or low temperatures.
  • This object is achieved according to the invention by a method for operating an electric motor, which is used as an electric servo drive in an electronic power steering system of a motor vehicle for power assistance and which has a number of magnetic elements and phase windings and is actuated and/or controlled by an electronic control unit of the electronic power steering system, wherein
  • the magnet temperature can advantageously be ascertained by way of a temperature model, which continuously determines or estimates the temperature of the magnetic elements during operation of the electric motor.
  • the magnet temperature can moreover be limited by a limitation of the phase currents of the electric motor, taking into account a predeterminable limit temperature of the magnetic elements.
  • the limit temperature of the at least one magnetic element can be a maximum temperature, which is not to be exceeded, or a minimum temperature, which is not to be fallen below.
  • the power loss of the electric motor, the torque created in the electric motor and/or opposing magnetic fields generated by the electrical current can be limited.
  • the limitation of the opposing magnetic fields plays a role in particular at very low temperatures when a minimum temperature of the at least one magnetic element is not to be fallen below.
  • the limitation can likewise be achieved with the aid of the temperature model.
  • the temperature model can have appropriate characteristic maps, characteristic curves, functions or tables for this purpose, which are ascertained in advance by experimentation, for example. Effective protection of the magnetic elements of the electric motor from demagnetization can be achieved by the measures according to the invention. As a result, the quality is considerably improved.
  • less expensive magnets having lower coercive field strength and/or lower demagnetization resistance can be employed.
  • the temperature model for determining the temperature of the at least one magnetic element of the electric motor receives, as input variables, at least one electrical current flowing in at least one of the phase windings of the electric motor, or a variable characterizing this electrical current, and/or at least one metrologically captured or calculated temperature that is present in a region of the electric servo drive.
  • the at least one temperature present in the region of the electric servo drive can be an ambient temperature prevailing in the electronic control unit, in particular on a printed circuit board of the electronic control unit, and/or in the region of an output stage of the electronic control unit.
  • the temperature model can utilize the phase currents and the temperature in the electronic control unit (ECU/Electronic Control Unit), for example on the printed circuit board thereof and/or in the output stage, as input variables.
  • these variables are, in any case, metrologically captured by the ECU for control purposes and/or for protection.
  • the determination of the magnet temperatures can thus be based on existing measured variables.
  • no additional sensors or the like are required.
  • the at least one temperature present in the region of the electric servo drive can be a temperature prevailing in at least one of the phase windings of the electric motor.
  • the temperature prevailing in at least one of the phase windings of the electric motor can be metrologically captured or calculated based on an electrical resistance in the at least one phase winding of the electric motor.
  • Existing electrical currents and voltages in the at least one phase winding of the electric motor can be used to calculate the electrical resistance.
  • a permanently excited synchronous machine preferably having three phase windings, can be used as the electric motor.
  • Electronic or electromechanical power steering systems typically have a permanently excited synchronous motor as the servo motor.
  • the invention relates to a method for operating an electronic power steering system of a motor vehicle provided with an electronic unit and to an electronic power steering system of a motor vehicle.
  • the method according to the invention for operating an electric motor and/or for operating an electronic power steering system of a motor vehicle is preferably implemented as a computer program on a control unit, or distributed on multiple control units, of the electronic power steering system, other solutions also being possible of course.
  • the computer program is stored for this purpose in a memory element of the at least one control unit.
  • the method is carried out by way of processing on a microprocessor of the control unit,
  • the computer program can be stored on a computer-readable data medium (disk, CD, DVD, hard drive, USB memory stick, SD card or the like) or an Internet server as a computer program product and can be transferred from there into the memory element of the control unit.
  • FIG. 1 shows a simplified schematic illustration of an electronic power steering system according to the invention, which is operated by a method according to the invention
  • FIG. 2 shows a simplified schematic to illustrate the method according to the invention for operating an electric motor.
  • FIG. 1 shows an electronic or electromechanical power steering system 1 according to the invention of a motor vehicle, which is not shown, in a highly simplified illustration.
  • the electronic power steering system 1 comprises a steering handle 2 designed as a steering wheel.
  • the steering wheel 2 is connected to a steering gear 4 by way of a steering column or universal shaft 3 .
  • the steering gear 4 is used to convert a rotational angle of the universal shaft 3 into a steering angle ⁇ Fm of steerable wheels 5 a , 5 b of the motor vehicle.
  • the steering gear 4 comprises a steering rack 6 and a pinion 7 for this purpose, the universal shaft 3 engaging on the pinion.
  • the electronic power steering system 1 further includes an electric servo drive 8 , which is used in particular for variable torque assistance.
  • the electric servo drive 8 comprises an electric motor 9 for implementing the torque assistance by way of a belt drive 10 .
  • the belt drive 10 comprises a drive pinion and a pulley for transmitting the torque assistance by way of a recirculating ball gear (not shown in FIG. 1 ) to the steering rack 6 of the electronic power steering system 1 .
  • an electronic control unit 11 for actuating and/or controlling the electric motor 9 is provided.
  • the invention will be described hereafter based on an electronic power steering system 1 comprising a belt drive 10 and a separate recirculating ball gear for transmitting the assistance force to the steering rack 6 , as is known from DE 100 52 275 A1, for example.
  • identical implementations according to the invention can be achieved for additional electrical steering system technologies having torque or steering assistance through minor modifications.
  • the electric motor can also be a superposition angle actuator, if the power steering system according to the invention is a superimposed steering system (not shown).
  • FIG. 2 shows a drastically simplified sketch of the actuation of the electric motor 9 by the electronic control unit 11 via motor phase lines 12 , which lead to phase windings (not shown) of the electric motor 9 .
  • the electric motor 9 comprises permanent magnets or magnetic elements 9 a.
  • a method for operating the electric motor 9 which is used as an electric servo drive 8 in the electronic power steering system 1 of the motor vehicle for power assistance, and which has a number of magnetic elements 9 a and phase windings, and is actuated and/or controlled by the electronic control unit 11 of the electronic power steering system 1 , can take place on the electronic control unit 11 , wherein
  • the limitation takes place in a functional block 14 .
  • the temperature model 13 and the limitation 14 can be implemented on the electronic control unit 11 , for example.
  • the temperature model 13 for determining the temperature ⁇ Magnet of the at least one magnetic element 9 a of the electric motor 9 receives, as input variables, at least one electrical current I U,V,W flowing in at least one of the phase windings of the electric motor 9 and/or at least one metrologically captured or calculated temperature ⁇ ECU that is present in a region of the electric servo drive 8 .
  • the at least one temperature present in the region of the electric servo drive 8 can be an ambient temperature ( ⁇ ECU ) prevailing in the electronic control unit 11 , in particular on a printed circuit board of the electronic control unit 11 , and/or in the region of an output stage of the electronic control unit 11 .
  • ⁇ ECU ambient temperature
  • the at least one temperature present in the region of the electric servo drive 8 can be a temperature prevailing in at least one of the phase windings of the electric motor 9 .
  • the temperature prevailing in at least one of the phase windings of the electric motor 9 can be metrologically captured or calculated based on an electrical resistance in the at least one phase winding of the electric motor 9 .
  • the electronic control unit 11 receives at least one maximum permitted electrical current I max flowing in the phase windings of the electric motor 9 from the limitation 14 for this purpose in the present exemplary embodiment.
  • the method according to the invention for operating the electric motor 9 and/or for operating the electronic power steering system 1 of the motor vehicle is preferably implemented as a computer program on the control unit, or distributed on multiple control units 11 , of the electronic power steering system 1 , other solutions also being possible of course.
  • the computer program is stored for this purpose in a memory element of the at least one control unit 11 .
  • the method is carried out by way of processing on a microprocessor ⁇ C of the control unit 11 .
  • the computer program can be stored on a computer-readable data medium (disk, CD, DVD, hard drive, USB memory stick, SD card or the like) or on an Internet server as a computer program product, and can be transferred from there into the memory element of the control unit 11 .

Landscapes

  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Transportation (AREA)
  • Mechanical Engineering (AREA)
  • Power Engineering (AREA)
  • Control Of Ac Motors In General (AREA)
  • Power Steering Mechanism (AREA)
  • Control Of Motors That Do Not Use Commutators (AREA)
  • Steering Control In Accordance With Driving Conditions (AREA)
  • Control Of Electric Motors In General (AREA)
US14/143,664 2013-01-30 2013-12-30 Method for operating an electric motor Active 2034-01-31 US9148079B2 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE102013201468.6A DE102013201468A1 (de) 2013-01-30 2013-01-30 Verfahren zum betrieb eines elektromotors
DE102013201468.6 2013-01-30
DE102013201468 2013-01-30

Publications (2)

Publication Number Publication Date
US20140210394A1 US20140210394A1 (en) 2014-07-31
US9148079B2 true US9148079B2 (en) 2015-09-29

Family

ID=51163536

Family Applications (1)

Application Number Title Priority Date Filing Date
US14/143,664 Active 2034-01-31 US9148079B2 (en) 2013-01-30 2013-12-30 Method for operating an electric motor

Country Status (4)

Country Link
US (1) US9148079B2 (de)
JP (1) JP2014148303A (de)
CN (1) CN103979009B (de)
DE (1) DE102013201468A1 (de)

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2014169061A (ja) * 2013-03-05 2014-09-18 Jtekt Corp 電動パワーステアリング装置
DE102015219815A1 (de) * 2015-10-13 2017-04-13 Brose Fahrzeugteile Gmbh & Co. Kommanditgesellschaft, Bamberg Verfahren zum Betrieb eines bürstenlosen Elektromotors und elektromotorische Pumpe
DE102016106431A1 (de) * 2016-04-08 2017-10-12 Ebm-Papst Mulfingen Gmbh & Co. Kg Temperaturüberwachung
DE102017201927A1 (de) 2017-02-08 2018-08-09 Robert Bosch Gmbh Verfahren und Vorrichtung zum Betreiben eines Lüfterantriebs
DE102018204159A1 (de) * 2018-03-19 2019-09-19 Robert Bosch Gmbh Verfahren zu Ansteuerung eines Elektromotors
DE102020117279A1 (de) 2020-07-01 2022-01-05 Dr. Ing. H.C. F. Porsche Aktiengesellschaft System und Verfahren zur Bestimmung der Magnettemperatur bei einer permanenterregten Synchronmaschine

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH1056799A (ja) 1996-06-05 1998-02-24 Denso Corp 発電装置
US6147465A (en) * 1999-03-25 2000-11-14 General Electric Company Microprocessor controlled single phase motor with external rotor having integral fan
DE10013711A1 (de) 2000-03-20 2001-10-11 Bosch Gmbh Robert Servounterstütztes Lenksystem eines Kraftfahrzeugs
DE10052275A1 (de) 2000-10-20 2002-05-16 Mercedes Benz Lenkungen Gmbh Kraftfahrzeugservolenkung mit elektrischem Servomoto und Zahnriemen
US7129660B2 (en) * 2002-03-20 2006-10-31 Toyota Jidosha Kabushiki Kaisha Motor-temperature estimation apparatus and motor control apparatus
US7248009B1 (en) * 2005-06-07 2007-07-24 Honeywell International Inc. Motor temperature control using estimated motor temperature based on motor power dissipation
JP2009165232A (ja) 2007-12-28 2009-07-23 Hitachi Ltd 回転電機の制御装置及び回転電機装置
US8310193B2 (en) * 2010-01-12 2012-11-13 Hamilton Sundstrand Corporation Minimum temperature control for electromechanical actuator

Family Cites Families (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE10212751A1 (de) * 2002-03-22 2003-10-02 Bosch Gmbh Robert Verfahren und Vorrichtung zur Ermittlung der Rotortemperatur bei einer PM-Synchronmaschine
JP2005012914A (ja) * 2003-06-19 2005-01-13 Koyo Seiko Co Ltd 電動機のドライバ
JP2005192325A (ja) * 2003-12-25 2005-07-14 Yaskawa Electric Corp 永久磁石電動機の減磁検出方法
JP2005218215A (ja) * 2004-01-29 2005-08-11 Nsk Ltd Ｐｍモータの駆動方法および温度推定方法
DE102005026439A1 (de) * 2005-06-08 2006-12-14 Siemens Ag Verfahren und Vorrichtung zum Steuern eines bürstenlosen Gleichstrommotors
JP4270196B2 (ja) * 2005-11-09 2009-05-27 トヨタ自動車株式会社 バッテリ状態診断装置
DE102005062588A1 (de) * 2005-12-27 2007-06-28 Robert Bosch Gmbh Verfahren zum Bestimmen der Magnettemperatur bei Synchronmaschinen
JP2008168669A (ja) * 2007-01-09 2008-07-24 Jtekt Corp 電動パワーステアリング装置
JP5211618B2 (ja) * 2007-10-01 2013-06-12 日本精工株式会社 モータ温度推定装置及びそれを搭載した電動パワーステアリング装置

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH1056799A (ja) 1996-06-05 1998-02-24 Denso Corp 発電装置
DE69707203T2 (de) 1996-06-05 2002-06-27 Denso Corp Generatorsystem mit einem, einen Permanentmagnet aufweisenden Generator
US6147465A (en) * 1999-03-25 2000-11-14 General Electric Company Microprocessor controlled single phase motor with external rotor having integral fan
DE10013711A1 (de) 2000-03-20 2001-10-11 Bosch Gmbh Robert Servounterstütztes Lenksystem eines Kraftfahrzeugs
DE10052275A1 (de) 2000-10-20 2002-05-16 Mercedes Benz Lenkungen Gmbh Kraftfahrzeugservolenkung mit elektrischem Servomoto und Zahnriemen
US7129660B2 (en) * 2002-03-20 2006-10-31 Toyota Jidosha Kabushiki Kaisha Motor-temperature estimation apparatus and motor control apparatus
US7248009B1 (en) * 2005-06-07 2007-07-24 Honeywell International Inc. Motor temperature control using estimated motor temperature based on motor power dissipation
JP2009165232A (ja) 2007-12-28 2009-07-23 Hitachi Ltd 回転電機の制御装置及び回転電機装置
US8310193B2 (en) * 2010-01-12 2012-11-13 Hamilton Sundstrand Corporation Minimum temperature control for electromechanical actuator

Also Published As

Publication number Publication date
DE102013201468A1 (de) 2014-07-31
CN103979009B (zh) 2017-12-05
US20140210394A1 (en) 2014-07-31
CN103979009A (zh) 2014-08-13
JP2014148303A (ja) 2014-08-21

Similar Documents

Publication Publication Date Title
US9148079B2 (en) Method for operating an electric motor
US10266198B2 (en) Motor control device
KR102023509B1 (ko) 모터 및 그의 센싱 마그네트
US10425025B2 (en) Power conversion device and motor drive apparatus
CN106330035B (zh) 旋转电机控制装置
WO2016143534A1 (ja) モータの駆動制御ユニット
EP2813414A1 (de) Elektrische servolenkvorrichtung
JP2012090383A5 (de)
US20200083826A1 (en) Fault tolerant permanent magnet dc motor drives
JP2008094342A (ja) 電動パワーステアリング装置
CN108352800A (zh) 电动助力转向装置及其控制方法
EP3504106B1 (de) Feuchtigkeitsmessung in einem elektromotor einer servolenkung eines fahrzeugs mit pull-up widerstand
US10532764B2 (en) Motor driving device, failure diagnosis method for motor driving device, and electric power steering apparatus using motor driving device
WO2015080021A1 (ja) 電気自動車の制御装置
US20040217729A1 (en) Electric power assist steering system and method of operation
JP2002345281A (ja) 電動パワーステアリング装置
CN110890856B (zh) 用于三相旋转机械设备的控制装置
WO2018198740A1 (ja) モータ駆動装置、および電動パワーステアリング装置
CN108352762B (zh) 具有冗余的电子子系统的机电式致动驱动器
KR101348569B1 (ko) 전동 파워스티어링 장치 및 그의 과열방지방법
JP2018098974A (ja) 電動パワーステアリング装置
KR101885098B1 (ko) 모터
KR102004348B1 (ko) Sbw 시스템에서 조향 반력 생성 장치 및 방법
US8131427B2 (en) Active resetting function for a steering wheel
US6847177B1 (en) Apparatus and method for determining rotor lamination shifts in an electric motor

Legal Events

Date Code Title Description
AS Assignment

Owner name: ZF LENKSYSTEME GMBH, GERMANY

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:KUEHNHOEFER, THOMAS;KRAUTSTRUNK, ALEXANDER;SIGNING DATES FROM 20140108 TO 20140110;REEL/FRAME:032166/0480

AS Assignment

Owner name: ROBERT BOSCH AUTOMOTIVE STEERING GMBH, GERMANY

Free format text: CHANGE OF NAME;ASSIGNOR:ZF LENKSYSTEME GMBH;REEL/FRAME:035749/0247

Effective date: 20150311

STCF Information on status: patent grant

Free format text: PATENTED CASE

MAFP Maintenance fee payment

Free format text: PAYMENT OF MAINTENANCE FEE, 4TH YEAR, LARGE ENTITY (ORIGINAL EVENT CODE: M1551); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY

Year of fee payment: 4

MAFP Maintenance fee payment

Free format text: PAYMENT OF MAINTENANCE FEE, 8TH YEAR, LARGE ENTITY (ORIGINAL EVENT CODE: M1552); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY

Year of fee payment: 8